Answers Database

BOUNDARY SCAN(JTAG): TAP Instructions not available if /PROG is held lowin XC4K/XC5K


Record #993

Product Family:  Hardware

Product Line:  4000

Problem Title:
BOUNDARY SCAN(JTAG): TAP Instructions not available if /PROG is held
lowin XC4K/XC5K



Problem Description:
Keywords: program, instructions, xc4000, jtag, boundary scan, xc5200

Urgency: standard

General Description: Which TAP instructions are available in XC4K/XC5K
FPGAs if the /PROGRAM pin is held low befor the device has been cofigured?


Solution 1:

If the /PROGRAM pin is held low, then the following boundary
scan instructions are not available in the XC4K/XC5K families:

readback
configure
extest

If the /PROGRAM pin is pulled low at any time, it will disrupt all
boundary scan operations as it effectively resets the TAP controller.



End of Record #993